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KevinEadyKevinEady
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Add node-addon-api async iterator example (#195)
* Add async iterator example * Add example for threadsafe-async-iterator
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‎async-iterator/node-addon-api/CMakeLists.txt‎

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project (example)
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include_directories(${CMAKE_JS_INC} node_modules/node-addon-api/)
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cmake_minimum_required(VERSION 3.18)
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set(CMAKE_CXX_STANDARD 20)
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set(CMAKE_CXX_STANDARD_REQUIRED ON)
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include_directories(${CMAKE_JS_INC})
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file(GLOB SOURCE_FILES "*.cc")
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add_library(${PROJECT_NAME} SHARED ${SOURCE_FILES} ${CMAKE_JS_SRC})
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set_target_properties(${PROJECT_NAME} PROPERTIES PREFIX "" SUFFIX ".node")
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target_link_libraries(${PROJECT_NAME} ${CMAKE_JS_LIB})
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# Include Node-API wrappers
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execute_process(COMMAND node -p "require('node-addon-api').include"
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WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
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OUTPUT_VARIABLE NODE_ADDON_API_DIR
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)
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string(REGEX REPLACE "[\r\n\"]" "" NODE_ADDON_API_DIR ${NODE_ADDON_API_DIR})
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target_include_directories(${PROJECT_NAME} PRIVATE ${NODE_ADDON_API_DIR})
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# define NAPI_VERSION
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add_definitions(-DNAPI_VERSION=6)

‎async-iterator/node-addon-api/example.cc‎

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#include <napi.h>
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#include <memory>
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using namespace Napi;
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class AsyncIteratorExample : public ObjectWrap<AsyncIteratorExample> {
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public:
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AsyncIteratorExample(const CallbackInfo& info)
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: ObjectWrap<AsyncIteratorExample>(info),
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_from(info[0].As<Number>()),
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_to(info[1].As<Number>()) {}
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static Object Init(Napi::Env env, Napi::Object exports) {
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Napi::Function func = DefineClass(
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env,
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"AsyncIteratorExample",
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{InstanceMethod(Napi::Symbol::WellKnown(env, "asyncIterator"),
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&AsyncIteratorExample::Iterator)});
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exports.Set("AsyncIteratorExample", func);
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return exports;
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}
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Napi::Value Iterator(const CallbackInfo& info) {
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auto env = info.Env();
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auto iteratorObject = Napi::Object::New(env);
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iteratorObject["current"] = Number::New(env, _from);
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iteratorObject["last"] = Number::New(env, _to);
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auto next = Function::New(env, [](const CallbackInfo& info) {
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auto env = info.Env();
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auto deferred =
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std::make_shared<Promise::Deferred>(Promise::Deferred::New(env));
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auto iteratorObject = info.This().As<Object>();
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auto callback = Function::New(
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env,
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[=](const CallbackInfo& info) {
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auto env = info.Env();
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auto value = Object::New(env);
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auto iteratorObject = info.This().As<Object>();
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auto current =
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iteratorObject.Get("current").As<Number>().Int32Value();
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auto last = iteratorObject.Get("last").As<Number>().Int32Value();
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auto done = current > last;
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if (done) {
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value["done"] = Boolean::New(env, true);
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} else {
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value["done"] = Boolean::New(env, false);
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value["value"] = Number::New(env, current);
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iteratorObject["current"] = Number::New(env, current + 1);
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}
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deferred->Resolve(value);
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},
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"next");
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env.Global()
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.Get("setTimeout")
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.As<Function>()
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.Call({callback.Get("bind").As<Function>().Call(callback,
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{iteratorObject}),
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Number::New(env, 1000)});
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return deferred->Promise();
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});
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iteratorObject["next"] =
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next.Get("bind").As<Function>().Call(next, {iteratorObject});
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return iteratorObject;
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}
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private:
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int _from;
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int _to;
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};
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Napi::Object Init(Napi::Env env, Object exports) {
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AsyncIteratorExample::Init(env, exports);
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return exports;
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}
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NODE_API_MODULE(example, Init)

‎async-iterator/node-addon-api/index.js‎

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const { AsyncIteratorExample } = require('bindings')('example');
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async function main(from, to) {
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const iterator = new AsyncIteratorExample(from, to);
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for await (const value of iterator) {
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console.log(value);
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}
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}
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/*
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// The JavaScript equivalent of the node-addon-api C++ code for reference
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async function main(from, to) {
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class AsyncIteratorExample {
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constructor(from, to) {
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this.from = from;
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this.to = to;
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}
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[Symbol.asyncIterator]() {
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return {
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current: this.from,
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last: this.to,
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next() {
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return new Promise(resolve => {
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setTimeout(() => {
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if (this.current <= this.last) {
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resolve({ done: false, value: this.current++ });
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} else {
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resolve({ done: true });
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}
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}, 1000)
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});
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}
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}
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}
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}
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const iterator = new AsyncIteratorExample(from, to);
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for await (const value of iterator) {
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console.log(value);
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}
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}
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*/
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main(0, 5)
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.catch(e => {
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console.error(e);
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process.exit(1);
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});

‎async-iterator/node-addon-api/package.json‎

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{
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"name": "async-iterator-example",
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"version": "0.0.0",
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"description": "Async iterator example using node-addon-api",
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"main": "index.js",
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"private": true,
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"dependencies": {
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"bindings": "^1.5.0",
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"cmake-js": "^6.3.0",
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"node-addon-api": "^5.0.0"
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},
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"scripts": {
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"test": "node index.js",
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"install": "cmake-js compile"
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}
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}

‎threadsafe-async-iterator/node-addon-api/CMakeLists.txt‎

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project (example)
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include_directories(${CMAKE_JS_INC} node_modules/node-addon-api/)
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cmake_minimum_required(VERSION 3.18)
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set(CMAKE_CXX_STANDARD 20)
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set(CMAKE_CXX_STANDARD_REQUIRED ON)
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include_directories(${CMAKE_JS_INC})
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file(GLOB SOURCE_FILES "*.cc")
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add_library(${PROJECT_NAME} SHARED ${SOURCE_FILES} ${CMAKE_JS_SRC})
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set_target_properties(${PROJECT_NAME} PROPERTIES PREFIX "" SUFFIX ".node")
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target_link_libraries(${PROJECT_NAME} ${CMAKE_JS_LIB})
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# Include Node-API wrappers
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execute_process(COMMAND node -p "require('node-addon-api').include"
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WORKING_DIRECTORY ${CMAKE_SOURCE_DIR}
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OUTPUT_VARIABLE NODE_ADDON_API_DIR
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)
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string(REGEX REPLACE "[\r\n\"]" "" NODE_ADDON_API_DIR ${NODE_ADDON_API_DIR})
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target_include_directories(${PROJECT_NAME} PRIVATE ${NODE_ADDON_API_DIR})
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# define NAPI_VERSION
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add_definitions(-DNAPI_VERSION=6)

‎threadsafe-async-iterator/node-addon-api/example.cc‎

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#include <napi.h>
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#include <condition_variable>
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#include <functional>
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#include <memory>
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#include <mutex>
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#include <optional>
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#include <thread>
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using namespace Napi;
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class ThreadSafeAsyncIteratorExample
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: public ObjectWrap<ThreadSafeAsyncIteratorExample> {
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public:
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ThreadSafeAsyncIteratorExample(const CallbackInfo& info)
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: ObjectWrap<ThreadSafeAsyncIteratorExample>(info),
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_current(info[0].As<Number>()),
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_last(info[1].As<Number>()) {}
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static Object Init(Napi::Env env, Napi::Object exports);
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Napi::Value Iterator(const CallbackInfo& info);
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private:
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using Context = ThreadSafeAsyncIteratorExample;
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struct DataType {
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std::unique_ptr<Promise::Deferred> deferred;
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bool done;
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std::optional<int> value;
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};
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static void CallJs(Napi::Env env,
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Function callback,
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Context* context,
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DataType* data);
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using TSFN = TypedThreadSafeFunction<Context, DataType, CallJs>;
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using FinalizerDataType = void;
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int _current;
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int _last;
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TSFN _tsfn;
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std::thread _thread;
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std::unique_ptr<Promise::Deferred> _deferred;
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// Thread-safety
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std::mutex _mtx;
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std::condition_variable _cv;
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void threadEntry();
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static void FinalizerCallback(Napi::Env env,
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void*,
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ThreadSafeAsyncIteratorExample* context);
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};
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Object ThreadSafeAsyncIteratorExample::Init(Napi::Env env,
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Napi::Object exports) {
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Napi::Function func =
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DefineClass(env,
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"ThreadSafeAsyncIteratorExample",
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{InstanceMethod(Napi::Symbol::WellKnown(env, "asyncIterator"),
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&ThreadSafeAsyncIteratorExample::Iterator)});
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exports.Set("ThreadSafeAsyncIteratorExample", func);
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return exports;
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}
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Napi::Value ThreadSafeAsyncIteratorExample::Iterator(const CallbackInfo& info) {
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auto env = info.Env();
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if (_thread.joinable()) {
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Napi::Error::New(env, "Concurrent iterations not implemented.")
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.ThrowAsJavaScriptException();
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return Napi::Value();
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}
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_tsfn =
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TSFN::New(info.Env(),
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"tsfn",
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0,
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1,
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this,
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std::function<decltype(FinalizerCallback)>(FinalizerCallback));
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// To prevent premature garbage collection; Unref in TFSN finalizer
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Ref();
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// Create thread
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_thread = std::thread(&ThreadSafeAsyncIteratorExample::threadEntry, this);
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// Create iterable
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auto iterable = Napi::Object::New(env);
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iterable["next"] =
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Function::New(env, [this](const CallbackInfo& info) -> Napi::Value {
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std::lock_guard<std::mutex> lk(_mtx);
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auto env = info.Env();
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if (_deferred) {
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Napi::Error::New(env, "Concurrent iterations not implemented.")
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.ThrowAsJavaScriptException();
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return Napi::Value();
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}
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_deferred = std::make_unique<Promise::Deferred>(env);
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_cv.notify_all();
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return _deferred->Promise();
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});
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return iterable;
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}
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void ThreadSafeAsyncIteratorExample::threadEntry() {
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while (true) {
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std::unique_lock<std::mutex> lk(_mtx);
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_cv.wait(lk, [this] { return this->_deferred != nullptr; });
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auto done = _current > _last;
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if (done) {
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_tsfn.BlockingCall(new DataType{std::move(this->_deferred), true, {}});
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break;
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} else {
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std::this_thread::sleep_for(
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std::chrono::seconds(1)); // Simulate CPU-intensive work
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_tsfn.BlockingCall(
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new DataType{std::move(this->_deferred), false, _current++});
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}
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}
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_tsfn.Release();
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}
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void ThreadSafeAsyncIteratorExample::CallJs(Napi::Env env,
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Function callback,
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Context* context,
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DataType* data) {
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if (env != nullptr) {
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auto value = Object::New(env);
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if (data->done) {
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value["done"] = Boolean::New(env, true);
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} else {
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value["done"] = Boolean::New(env, false);
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value["value"] = Number::New(env, data->value.value());
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}
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data->deferred->Resolve(value);
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}
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if (data != nullptr) {
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delete data;
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}
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}
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void ThreadSafeAsyncIteratorExample::FinalizerCallback(
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Napi::Env env, void*, ThreadSafeAsyncIteratorExample* context) {
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context->_thread.join();
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context->Unref();
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}
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Napi::Object Init(Napi::Env env, Object exports) {
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ThreadSafeAsyncIteratorExample::Init(env, exports);
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return exports;
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}
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NODE_API_MODULE(example, Init)

‎threadsafe-async-iterator/node-addon-api/index.js‎

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const { ThreadSafeAsyncIteratorExample } = require('bindings')('example');
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async function main(from, to) {
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const iterator = new ThreadSafeAsyncIteratorExample(from, to);
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for await (const value of iterator) {
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console.log(value);
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}
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}
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main(0, 5)
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.catch(e => {
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console.error(e);
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process.exit(1);
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});

‎threadsafe-async-iterator/node-addon-api/package.json‎

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{
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"name": "threadsafe-async-iterator-example",
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"version": "0.0.0",
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"description": "Async iterator example with threadsafe functions using node-addon-api",
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"main": "index.js",
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"private": true,
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"dependencies": {
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"bindings": "^1.5.0",
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"cmake-js": "^6.3.0",
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"node-addon-api": "^5.0.0"
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},
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"scripts": {
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"test": "node index.js",
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"install": "cmake-js compile"
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}
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}

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